The U.S. Census Bureau says that the average household size slipped to 2.57 people in 2003 from 3.14 in 1970. According to “America's Families and Living Arrangements: 2003,” one-third of households have only two members. Experts attribute the drop in household size to changes in divorce and mortality rates, the aging population, a decline in fertility, and delayed marriage plans.

Source: CBS Marketwatch